Choosing Apple rootstocks

What is a rootstock? The majority of fruit trees that people grow today are grafted trees. A grafted tree is composed of two parts - the rootstock and the scion. The scion is most of the above ground tree, and is usually referred to as the variety of the fruit. The rootstock is mostly, well the roots - and a few inches of trunk above ground where it meets the scion at the graft union. Trees are grafted so that we can choose the scion and know what variety of fruit we'll get, rather than leave it to genetic chance of what a seedling would produce. Over time, different rootstocks have been developed that determine tree size, determine precocity (how soon the tree will bear fruit), offer disease resistance, and carry other characteristics.

Choosing a rootstock. The choice of rootstock may be the most influential factor in how your tree will grow, especially in apples. The list of rootstocks for stone fruits rather small - so the choices are a bit easier. But the list of apple rootstocks is long. This can make it daunting to choose, but ultimately having lots of rootstock options is a blessing. People often refer to rootstocks as either dwarf, semi-dwarf, or standard size as if there only 3 sizes. But for apples, there are many different rootstocks with different size characteristics. When choosing a rootstock, the primary considerations are:

How big do you want your tree to be?

How soon do you want to get a crop of apples?

Does your planting site or climate have specific issues that need to be considered?

Do you need to consider disease resistance?

Tree size and precocity. Tree size has an inverse relationship with precocity, meaning that the larger the size of the tree, the longer it will be before the tree produces a full crop. Large trees put their energy into vegetative growth for many years to grow into their full shape before they start spending energy on developing fruit buds and making fruit. The more dwarfing the rootstock, the earlier in life the tree will begin making fruits - because it's not planning to spend its energy growing 25 feet tall.

I am a proponent of trees on the more dwarfing size for most backyard growers. I think most people want to eat apples from their tree sooner rather than later, and don't have tons of space. If you do have tons of space, you can plant lots of different varieties if you use a more dwarfing rootstock.

The case for M26 rootstock. M26 comes from the M, or EMLA series or rootstocks developed at the East Malling Research Station in England. There are many dwarfing apple rootstocks, and M26 is roughly the largest of the dwarf rootstocks - producing a tree that is 8 to 12 feet tall. Trees that are more dwarfing than M26 will generally not be free-standing. Many modern orchards now grow extremely dwarfing trees, and they grow them on big trellis systems. Using dwarfs allows orchards to sell a crop in a shorter time frame, which is a big deal when large scale apple businesses have millions invested in a new planting.

But for home gardens and backyard orchards, I like M26 because it a relatively small tree, quick to produce fruit and doesn't need a trellis. M26 may need some support, like a single stake. Mine have grown out of needing a stake after 1-2 years. I have generally gotten good crops after 2 years with my M26 trees, which is a great turnaround time in my opinion. With my M111 tree, the largest semi-dwarf in the M series, I am going on year 6 without getting a good crop. All rootstocks have their pros and cons, and dwarfing trees need more water than large trees due to their smaller root systems. M26 is subject to burr knots, though I can't say that's been a big deal to me.

Excellent fruit bud development on Zestar! on M26, planted 2 years ago.

The case for M7 rootstock. Along with M26, M7 is my other favorite apple rootstock. In size, M7 is the next step up from M26, with an average height of 10-15 feet. It is free-standing, has moderate resistance to fireblight and crown rot, and is not as precocious as M26 but still produces fruit in 2-4 years. M7 is subject to suckering, meaning the rootstock likes to send up sprouts from the base of the tree that have to be pruned off. It's not much of an issue, unless you plan to leave your trees delinquent for years at a time. Overall, it's hard to go wrong with M7.

Considering M111 rootstock. The majority of apple trees that I see at local nurseries come on M111 rootstock, and personally I do not think it's always the best choice for a backyard grower. It's the largest of the semi-dwarf rootstocks, growing an average of 15-20 feet tall. The next size up would be a seedling, a 30 foot tall tree. Because of its size, M111 will take longer to produce fruit - average of 5 years, but it can be longer. Of course, M111 has its upsides. Because of its larger roots, it will be more tolerant of drought and it's noted to tolerate a wide range of soil types. If you want a tree for your kids to climb in, M111 size or seedling size will be much better for that than more dwarfing trees. But if you're looking for getting fruit relatively soon, an easily managed tree size with fruit that you can reach without a ladder - I don't think M111 is the best choice for that. So why is it so popular at nurseries? It is probably harder to kill, because it's more likely to survive if you don't give it enough water. If you want a fairly large tree, and you are happy to wait patiently for fruit, M111 can be a good choice. If you want to plant a more dwarfing tree like M26 or M7 - just remember that it needs water, especially in the early years.

Geneva series rootstocks, G890 and G969. Wait, there's more? Yeah there's actually a ton more that I won't even get into. I'm only touching on a few of the rootstocks that I think are most relevant to backyard growers. But it wouldn't be complete without mentioning the Geneva series. The Geneva series of rootstocks was developed at Cornell University, with a particular emphasis on disease resistance. You can choose scions that have disease resistance, which is a good idea, but the intention of the Geneva series is to impart disease resistance to all trees regardless of the scion chosen. Geneva series were developed for resistance to fire blight, crown rot, wooly apple aphid, and replant disease (an issue mostly relevant to commercial plantings).

Just like the M series, there are many size variations of the Geneva series. G969 produces a tree that is 10-15 ft tall, and has been noted to show some of the highest fruit bud to wood ratio in a rootstock efficiency study. G890 produces an 11-16 ft tall tree. Both are supposed to be free-standing trees, and are described as precocious - producing fruit in 2-3 years. The main downsides of Geneva series is that there's not as much information available on them. They are more utilized in commercial growing than backyard orchards, so there's just not as much experience to draw from. They seem to have a lot of potential, given that disease resistance can cut down on time managing problems with your trees. I have a few trees on these rootstocks, but they are only 1-2 years old. Some concerns with Geneva rootstocks have been with weak graft unions, causing even mature trees to break at the graft union. This has been most noted with G41, and has not been noted in G890 or G969. Still, if you live in a place that gets heavy winds - it could be worth sticking to M series rootstocks.

On Backyard Orchard Culture. A lot of nursery tags now say something like "tree height can be kept to any height with summer pruning" regardless of the rootstock determined tree size. Personally, I think that's rather misleading. You can limit tree height with summer pruning to a degree. And I'm sure there are people out there with an M111 rootstock tree that have kept it to 8 ft tall. But that doesn't mean it's the best idea. If a tree wants to be 20 ft tall, and you want it to be 10 - you're going to be battling that tree for life. It will keep putting energy into vegetative growth to try to be big, and you'll keep cutting it back to make it small. And eventually you might wear it out and keep it small. But it will not be putting energy into fruit bud formation, it will be fighting you for years before it starts doing that. So if you want an 8 ft tall tree, much better to choose a tree that wants to be 8-12 feet tall and work with it. It will make fruit much faster, and it will probably be a better looking tree in the end.

Sourcing trees with specific rootstocks. If you can't find the rootstock you're looking for locally, there are many good online nurseries that ship bare root trees. Shipping trees might seem absurd, but I've done it a bunch and it generally works just fine. One Green World and Raintree are some options.

Remember, opinions are like........well you know, everyone's got one. These are just mine.